When are they going to just seal off an area so it's self-driving vehicles only, and test them there? In a 100% self driving environment, edge cases are probably much easier to reason about. And if the future is 100% self driving, they should probably get some training data from that environment anyway.
With bicycles and pedestrians sharing the common roads, a 100% self driving environment anywhere but the freeway is never going to happen though. They need to be able to handle the chaos.
